The invention relates to improvements in methods of and in apparatus for delivering photosensitive materials, such as webs of convoluted printing paper, to a processing machine, especially to a printer. More particularly, the invention relates to improvements in methods of and in apparatus for automatically delivering photosensitive material to a printer or another processing machine at the frequency at which successive webs of convoluted photosensitive material are processed or consumed in the machine.
Commonly owned U.S. Pat. No. 4,469,291 to Treiber et al. discloses an apparatus which serves to transfer webs of photosensitive material between discrete cassettes and a processing machine, e.g., a photographic copying machine. Cassettes which can be used in the apparatus of Treiber et al. are disclosed in commonly owned U.S. Pat. No. 4,466,579 to Nitsch et al. A drawback of apparatus which are used to withdraw webs of photosensitive material from, or to introduce such material into, discrete cassettes is that each and every roll consisting of a core and a web of convoluted photosensitive material on the core must be confined in a discrete housing and the support for the core must be combined with braking means and other components which contribute tho the bulk and cost of the cassettes and of the entire apparatus. In addition, it is necessary to continuously monitor the cassette which is in the process of delivering a web to or in the process of receiving a web from a printer or another machine. This also contributes to the cost of treatment of such webs. Empty cassettes must be individually replaced with filled cassettes and vice versa.
In accordance with another prior proposal, several cassettes for discrete rolls of photosensitive material are mounted on a vertical turntable which is indexable to move successive empty cassettes to optimum positions for reception of webs or to move successive filled cassettes to optimum positions for delivery of their webs to a processing machine. Since each cassette is designed to contain a long web of photosensitive material, the combined bulk of a number of cassettes contributes to often excessive space requirements of such apparatus and renders it necessary to employ a heavy turntable which must be indexed by a strong motor with attendant consumption of substantial amounts of energy. It is further necessary to provide expensive accelerating, decelerating and braking means for the turntable and the cassettes thereon.
In order to avoid the need for an exchange of individual, normally wheel-mounted, cassettes of the type disclosed in the aforementioned U.S. Pat. No. 4,466,579 to Nitsch et al., it was already proposed to dispose several mobile cassettes at each side of a printer and to automatically shift freshly emptied and/or freshly filled cassettes from positions for withdrawal of photosensitive material or for introduction of photosensitive material. Alternatively, a control system can be designed to regulate the operation of a mobile web threading unit which can be shifted from cassette to cassette at the printing station. Reference may be had to commonly owned U.S. patent applications Ser. Nos. 175,160 now U.S. Pat. No. 4,853,742 (filed Mar. 30, 1988 by Payrhammer et al.) and 175,161 now U.S. Pat. No. 4,843,430 (filed Mar. 30, 1988 by Huber et al.). Such apparatus contribute significantly to automation of the operation; however, they still employ discrete cassettes for rolls of convoluted photosensitive material which contributes to the cost and bulk of the apparatus.
Commonly owned German patent application No. 37 34 896 describes another proposal according to which webs of photosensitive material must be convoluted onto specially designed cores. This, too, entails a pronounced increase of the cost due to the need for specially designed cores. Moreover, such apparatus cannot accept rolls wherein the webs of photosensitive material are convoluted on conventional cores.